Earth boring drill bit



y 14, 1964 E. w. ENGLE ETAL EARTH BORING DRILL BIT 3 S eats-Sheet 1INVENTORS. EDGAR IV. ENGLE JAMES L FOSTER, JR.

Fig. 1

Filed May 16, less A TTOR/VE V5 uly 14, 1964 E. w. ENGLE ETAL EARTHBORING DRILL BIT 3 Sheets-Sheet 2 Filed May 16, 1965 INVENTORS. EDGAR MENGLE JAMES L. F057ER,JR.

ATTORNEW.

J1l1y'14, 1964 E. w. ENGLE ETAL I 3,140,743

EARTH BORING DRILL BIT Filed May 16, 1963 INVENTORS. EDGAR 11 54/045 BY.uuss 4. FOSTE/LJR.

United States Patent 3,140,748 EARTH EORING DRILL BIT Edgar W. Eagle andJames L. Foster, 3n, Laughlintown,

Pa, assignors to Kennainetal Inc., Latrobe, Pa., a corporation ofPennsylvania Filed May 16, 1963, Ser. No. 280,969 6 Claims. (til.175410) This invention relates to an earth boring drill bit of the rigidbearingless type, known as a drag bit. Although the emphasis in thisapplication is on the use of such a bit in drilling through earthformations for oil, gas, and the like, it is to be understood that theinvention is also useful in other earth boring applications, includingmining and quarrying.

Oil well drill bits are subjected to a great variety of operatingconditions. The formations they are called upon to penetrate, the typeof rigs used to drive them, the nature of the various components in thedrill string, the hydraulic system used, and the applied loads androtary speeds, all vary widely. The interaction of these variablesaffects bit life, measured either in hours of drilling operation or infeet of earth penetration, and it also affects the rate of penerationand the ability of the bit to drill through hard rock formations.

Drilling bits that are characterized by long life under the aboveoperating conditions, and that are also characterized by rapidpenetration in a variety of formations from soft to hard, by lowfrequency of pulls, by maintenance of substantially full hole gauge andby limitation of hole deviation within allowable limits, are veryvaluable to the petroleum industry. In addition, a satisfactory bitshould be self-sharpening; and it should also have a certain geometry topenetrate rapidly through various formations. the bit, it should beretained as the bit wears in use. In some cases, however, the desiredbit geometry is created only as the bit wears in use and, once created,should be retained during further use.

It is accordingly among the objects of this invention to provide arotatable drag bit that will have the desirable characteristicsmentioned above, including the capability of drilling in hard formationsat a faster rate over longer periods of time than is obtainable withconventional bits, that will maintain a substantially full gauge hole inhard and abrasive rock formations, that will be self-sharpening, andthat will have a wear pattern in use that will retain or create adesirable geometry for the bit.

The foregoing and other objects of the invention will be apparent fromthe following description of a preferred embodiment, in connection withthe accompanying drawings, in which FIG. 1 is an end view of a drag bitmade in accordance with this invention;

FIG. 2 is a side elevation of the bit of FIG. 1;

FIG. 3 is a front elevation of this same bit;

FIG. 4 is a fragmentary section along the line IVIV of FIG. 1;

FIG. 5 is an end view of a modified form of drag bit;

FIG. 6 is a front elevation of the bit of FIG. 5;

FIG. 7 is a side elevation of the same bit;

FIG. 8 is a fragmentary section along the line VIII-VIII of FIG. 5;

FIG. 9 is a fragmentary end view of a further modified form of drag bit;and

FIG. 10 is a section along the line XX of FIG. 9.

The drill bit of the present invention is adapted to be rotated aboutits longitudinal axis and includes a body that can be attached to thedrill string by conventional means and a plurality of drag bit wingssupported by the body. Each wing extends radially beyond the body toprovide a hole-gauging face substantially in the form of Where thisgeometry is initially present in 3,146,748 Patented July 14, 1964 "ice aportion of a cylindrical surface that subtends, for the reasonshereinafter discussed, a substantial circumferential arc. Each wing alsoextends axially ahead of the body to provide an end drilling face havingthe general form of a sector of an annulus. Lastly, each wing has anextended, generally plane, forward face, on which is mounted a layer ofcemented tungsten carbide, or other suitable hard material, which notonly protects the forward face from wear (for example, from erosion bydrilling muds), but also provides extremely hard cutting edges at thejunctions of the forward face with the ganging and end faces. Inaddition, cemented tungsten carbide inserts are embedded in each wingbehind its forward face, with portions of the inserts exposed on thegauging and end faces. These inserts serve the important purpose oflimiting the wear of the wing material that directly supports thecutting edges on the forward face, thereby to assure that those cuttingedges will be backed up by adequate material as the bit is used and soprevent their breakage and prolong their useful life. Moreover, theexposed portions of the inserts on the gauging and end faces supplementthe cutting action of the forward face cutting edges and, if necessary,can perform that function alone; they have also other useful functionsto be described herein.

Referring to the drawings, the bit of this invention includes a body 1of steel or other suitably strong material, which is adapted to beattached by conventional means (not shown) to the end of a rotatingdrill string. Formed integrally with the body, or secured thereto by anysuitable means, are a plurality of drag bit wings 2 which aresubstantially symmetrically disposed about the longitudinal axis of thebit and are made of steel or other suitably strong material. These wingsextend radially beyond the body to form a hole-gauging face 3 that issubstantially a portion of a cylindrical surface generated by a linerotated about the longitudinal axis of the bit, or about a line parallelto that axis. This face extends circumferentially over a substantialare, preferably of at least 10 sufficient to provide a strong base andsupport for the cutting elements. The exact arcuate extent of thegauging face 3 will depend in part on the diameter of the drill (beinggreater for smaller diameter drills) and on the types of formations tobe drilled. Each wing also extends axially ahead of the body to form anend drilling surface 4, which is generally in the form of a sector of anannulus, of which the outer arcuate edge 6 coincides with an edge of thecylindrical gauging face and the central inner edge 7 is formed by theinner arc of the annulus. Each wing also has a forward face 8 ofextended area and of generally planar form. This face may, if desired,be disposed in two planes, as shown in FIGS. 1-3, or in a single plane,as shown in FIGS. 4-7, these planes being generally parallel orsubstantially parallel to the longitudinal axis of the bit.

Each forward face 8 is substantially covered by a layer of a suitablehard alloy, preferably in the form of a plurality of plates 9 ofcemented tungsten carbide. These plates may be brazed to the face 8; or,under certain conditions, a layer of other suitable hard material can bepuddled or welded on the face. The plates 9 are preferably of simplegeometrical form, such as squares or rectangles, to provide straight endcutting edges 11 and side cutting edges 12. The thickness of the plateswill vary, depending up on the size of the bit, the formations to bepenetrated, etc. The plates also serve to protect the face from erosionby abrasive particles entrained in the drilling fluid, this fluid beingpumped through openings 13 of nozzles 14, which are preferably made ofcemented tungsten carbide.

In the wing material behind the forward face are embedded a plurality ofcemented tungsten carbide inserts 16, which are so disposed that theytend to minimize wear of the wing material that supports the cuttingedges of the carbide plates on the forward face. These inserts may takea variety of forms, such as cylindrical rods or substantiallyrectangular right prisms, and may be embedded with their long axeseither parallel or inclined to the longitudinal axis of the bit, orextending radially of the bit. Further considerations that govern thelocation of these embedded inserts include the promotion and maintenanceof a desired bit geometry during prolonged drilling, such as, forexample, the promotion and maintenance of concentric arcuate grooves inthe drilling face of the bit, these fingering grooves helping tominimize undesirable gyrations of the bit. For example, in FIGS. 1-4,one group of inserts 17 is in the form of cylindrical plugs of cementedtungsten carbide embedded in the end drilling face and extendingparallel to the axis of the bit, and a second group of inserts 18 is inthe form of substantially right rectangular prisms embedded radially inthe gauging face and extending in a single row parallel to the axis ofthe bit. A third group of inserts 19 is in the form of cylindrical rodsthat lie in a second longitudinal plane disposed at an angle to theplane of the first two groups of inserts, and each insert of the thirdgroup is disposed at an angle of approximately 45 to the axis of thebit. The exposed portions of these last inserts are confined to thegauging face and to the intersection of that face and the end face, butadditional inserts may be inserted in this same plane in the end face,if desired, as shown by the broken line elements 21 in FIGS. 1 and 4.There is also shown in FIG. 4, by the broken line 22, an approximatetypical profile or contour of the end face after the bit has been usedfor a certain period of time. A second contour line 23 shows a typicalbit profile after the bit has been used for a still longer time. Asthese profile lines indicate, the end of the bit gradually assumes asomewhat conical shape, and there is a tendency for the wing materialbetween the embedded inserts to wear faster than the inserts themselvesto produce a desirable fingering configuration. The side cutting edgesof the forward face may be reinforced by an additional group of carbideinserts 24, which are disposed directly behind and in supporting contactwith the edge forming plates 9 of the forward face. The exposed portionsof these inserts are contoured to conform to the surface of the gaugingface.

In the modified form of bit shown in FIGS. -8, all of the embeddedcarbide inserts in the wings are in the form of spaced cylindrical rods,which are disposed in two main groups. Those inserts 26 on the end faceand on the adjacent portion of the gauging face are set at an angle of45 to the axis of the bit, with the inserts exposed on the end facelying in concentric circles about the bit axis and the inserts exposedon the gauging face lying in horizontal and vertical rows. However, onthat portion of the gauging face that is remote from the end face, theinserts 27 lie in horizontally staggered rows and extend radially of thewing and substantially normal to the axis of the bit. The insertarrangement in the first group of inserts 26 tends to promote thedevelopment of the fingering or grooving contour that helps to keep thebit properly aligned. That of the second group of inserts 27, where theinserts are staggered horizontally and the space between any two insertsin a vertical row is preferably less than the diameter of the insert inan adjacent vertical row, tends to avoid the grooving or fingeringconfigurations that is desirable elsewhere and provides a better andmore lasting gauging action to maintain hole size during drilling.

In FIGS. 9 and 10, the cemented tungsten carbide inserts are in thegeneral form of cylindrical rods of different diameters, all of whichare oriented parallel to the bit axis. The larger diameter inserts 31are embedded in slots in the gauging face, and each extends for the fulllength of that face and has its exposed portion contoured to conform tothe surface of that face. Inserts 31 supplement the gauging or sidecutting edge 12 of the forward face, as well as the radially outerportion of the end cutting edge 11 of that face. The smaller diameterinserts 32, which are disposed on a radial line inward of one of theinserts 31, supplement the end cutting edge 11 of the forward face.

It will be apparent to those skilled in the art that it is possible touse still other arrangements and dispositions of the cemented tungstencarbide inserts, it being the function of those inserts, (1) to limitwear and erosion of the end and gauging faces of the bit, so that thecemented tungsten carbide inserts on the forward faces will have anadequate depth of wing material to support them and (2) to act assupplemental cutting edges or points that cooperate wtih the cuttingaction of the forward face edges and, in the event those edges fail,take over their function. In addition, the inserts in the end face havea further important function. In deep well drilling, the clasticity ofthe drill string creates considerable percussive interaction between theend of the drill bit and the formation being drilled. Such percussiveaction permits the eX- posed ends of the carbide inserts to disintegratethe rock, without injury to the carbide inserts, because they are allwell embedded in a mass of strong material that gives them adequatesupport.

Among the advantages of using the heavy wing structure and the cementedtungsten carbide inserts, mounted in slots, recesses, or holes in thewings behind the forward faces, as herein described, is that the usefullife of carbide cutting edges on the forward faces is greatly increased,because such inserts not only limit wear of the material supportingthose edges, but also share in the cutting action. The inserts also arecapable of taking over the function of the carbide cutting edges on theforward faces, in the event those edges fail. It has been found thatcemented carbide cutting edges, if adequately supported in this way, canbe held in place without failure of the carbide itself or of the carbideto steel bond when subjected to loads that would cause such failure ifthe inserts were not present.

Another advantage of the present invention is that the embedded carbideelements in the wings may be so disposed that they cause the desired bitgeometry to be generated or retained as wear occurs, as, for example, afingering configuration may be generated to reduce bit gyration, as Wellas to assist in gaining a greater rate of penetration.

According to the provisions of the patent statutes, we have explainedthe principle of our invention and have illustrated and described whatwe now consider to represent its best embodiment. However, We desire tohave it understood that, within the scope of the appended claims, theinvention may be practiced otherwise than as specifically illustratedand described.

We claim:

1. A drilling bit of the drag bit type adapted to be rotated about itslongitudinal axis, the bit comprising: a body, a plurality of wingssupported by the body, each wing extending radially beyond the body toprovide a holegauging face in the form of a portion of a cylindricalsurface that subtends a substantial circumferential arc, each wing alsoextending axially ahead of the body to provide an end drilling face inthe form generally of a sector of an annulus, and each wing also havingan extended forward face of generally planar form, a layer of hard alloymaterial secured to each forward face to provide hard cutting edges atthe junctions of that face with the gauging and drilling faces, andcemented tungsten carbide inserts embedded in each wing behind theforward face with portions of the inserts exposed on the gauging anddrilling faces for limiting wear of the wing material supporting thecutting edges of the hard alloy material on the forward face and forsupplementing the cutting action of those edges.

2. Apparatus according to claim 1, in which the circum- O ferential arcsubtended by the gauging face of each Wing is at least 10.

3. Apparatus according to claim 1, in which the layer of hard alloymaterial secured to each forward face is in the form of a plurality ofplates of cemented tungsten carbide, the plates being arranged in aregular tessellation substantially covering said face.

4. Apparatus according to claim 1, in which the portions of the insertsexposed on the end drilling face are radially spaced to providepreferential arcuate grooving of the end face for increasing penetrationrate and for limiting gyration of the bit during drilling operations.

5. Apparatus according to claim 1, in Which the portions of the insertsexposed on the gauging face adjacent the end face are axially spaced toprovide preferential grooving of that part of the gauging face forincreasing penetration rate and for limiting gyration of the bit duringdrilling operations.

6. Apparatus according to claim 5, in which portions of the insertsexposed in the gauging face remote from the end face are disposed in astaggered array to prevent preferential grooving of that part of thegauging face during drilling operations.

References Cited in the file of this patent UNITED STATES PATENTS1,923,487 Howard Aug. 22, 1933 1,923,488 Howard Aug. 22, 1933 1,978,084Howard Oct. 23, 1934 2,693,938 Roberts Nov. 9, 1954 3,106,973Christensen Oct. 15, 1963 FOREIGN PATENTS 1,228,941 France Mar. 21, 1960

1. A DRILLING BIT OF THE DRAG BIT TYPE ADAPTED TO BE ROTATED ABOUT ITSLONGITUDINAL AXIS, THE BIT COMPRISING: A BODY, A PLURALITY OF WINGSSUPPORTED BY THE BODY, EACH WING EXTENDING RADIALLY BEYOND THE BODY TOPROVIDE A HOLEGAUGING FACE IN THE FORM OF A PORTION OF A CYLINDRICALSURFACE THAT SUBTENDS A SUBSTANTIAL CIRCUMFERENTIAL ARC, EACH WING ALSOEXTENDING AXIALLY AHEAD OF THE BODY TO PROVIDE AN END DRILLING FACE INTHE FORM GENERALLY OF A SECTOR OF AN ANNULUS, AND EACH WING ALSO HAVINGAN EXTENDED FORWARD FACE OF GENERALLY PLANAR FORM, A LAYER OF HARD ALLOYMATERIAL SECURED TO EACH FORWARD FACE TO PROVIDE HARD CUTTING EDGES ATTHE JUNCTIONS OF THAT FACE WITH THE GAUGING AND DRILLING FACES, ANDCEMENTED TUNGSTEN CARBIDE INSERTS EMBEDDED IN EACH WING BEHIND THEFORWARD FACE WITH PORTIONS OF THE INSERTS EXPOSED ON THE GAUGING ANDDRILLING FACES FOR LIMITING WEAR OF THE WING MATERIAL SUPPORTING THECUTTING EDGES OF THE HARD ALLOY MATERIAL ON THE FORWARD FACE AND FORSUPPLEMENTING THE CUTTING ACTION OF THOSE EDGES.